Accident Delays Saturn Launch

As NASA prepares to launch its largest space probe ever to the mystical ringed planet Saturn, exasperated scientists are scrambling to deal with anti-nuclear protesters as well as a launch pad accident at Cape Canaveral, Fla., that will delay the scheduled Oct. 6 liftoff.

NASA announced Wednesday that an overpowered air conditioner servicing the Cassini spacecraft tore a 2-inch rip in the insulation that protects the craft’s hitchhiking Huygens probe, which is due to land on Saturn’s planet-size moon, Titan. It is possible that the mishap sprayed foam particles that would contaminate Huygens’ delicate instruments, but scientists won’t know until they hoist the craft off the launch tower, remove the probe and clean it thoroughly.

Meanwhile, well-organized protesters concerned that an accident could send 72 pounds of highly radioactive plutonium that powers Cassini raining on Earth said they are planning everything from a news conference in Washington next week to planting themselves on the launch pad. The critics worry that Cassini could crash into Earth either during takeoff or a 1999 Earth fly-by, releasing cancer-causing plutonium particles into the atmosphere.

Scientists at the Jet Propulsion Laboratory, which directs the project, dismissed such concerns as unrealistic. These continuing troubles, they suggested, only detract attention from the object of the Cassini scientists’ affections--Saturn, arguably the most beautiful object in the solar system.

Girdled by intricately braided rings and surrounded by at least 18 icy satellites, Saturn today may look much like our solar system in its infancy. Its giant moon Titan may hide a solid surface underneath its thick orange smog, and perhaps seas of hydrocarbon soup of the type that gave rise to life on Earth.

“We don’t understand [why people are concerned],” said Cassini project science manager Ellis Miner, who added that he is far more worried about protesters “getting hurt” by alligators in the swamps surrounding the launch pad.

Plutonium-powered spacecraft are nothing new for NASA. The Viking missions to Mars as well as Voyager missions and Galileo spacecraft now orbiting Jupiter all relied on plutonium power sources. Even the little Mars rover Sojourner carries several grams of plutonium to keep it warm enough to function.

Three plutonium-carrying missions have failed--including the Russian Mars96 spacecraft, which never reached orbit, and is thought to have crashed somewhere in Bolivia. It is not known whether plutonium was released in those instances.

If Cassini does get off during the launch window ending Nov. 15, it will cruise toward the sixth planet from the sun for seven years, swinging twice by Venus, once by Earth and once by giant Jupiter to gather enough gravitational steam to reach its target.

Once there, it will take hundreds of thousands of images of airy Saturn (the lightest planet in the solar system), and the glittering lanes of icy particles that run rings around it like so many Southland freeways. (The Cassini spacecraft is named after the 17th century astronomer who discovered the largest “divider,” or gap, in the rings; the Huygens is named for the astronomer who discovered the rings and Titan.)

The complex ring system shares features with many spiral galaxies, and perhaps other solar systems, said Cassini Imaging Team Leader Carolyn Porco. As the billions of rocks, boulders and tiny particles in the rings are pushed and pulled by the gravitational forces of the moons, the rings knot and braid and spiral into intricate structures, even fanning out into spokes that appear and alter over time.

The big question, said Porco, is “how did [the rings] get there? How long will they stick around?”

Perhaps even more intriguing, giant Titan--the only moon in the solar system with an appreciable atmosphere--promises to be “an organic chemist’s dream,” said University of Tucson planetary scientist Jonathan Lunine. With an atmosphere four times denser than Earth’s, smog-covered Titan kept its surface well hidden during the Voyager fly-bys, but Cassini carries radar that can see through the clouds. Researchers believe parts of Titan’s surface could be solid, with seas and lakes of liquid methane and hydrocarbons that rain down from its soupy skies.

The frigid cold--minus 288 degrees Fahrenheit--would naturally sterilize any life out of existence, Lunine said. But it is possible that Titan was once on the road to life. “It’s the closest analogue we have to Earth before life began,” he said. Understanding the chemistry of Titan will tell us “how we came to be.”

Huygens will ride to Saturn attached to the 12,500-pound Cassini like a giant gilt barnacle. Once released, it will parachute to the ground where it is expected to survive long enough to transmit perhaps half an hour’s worth of data.

The six scientific instruments aboard the Huygens lander and nearly a dozen more aboard the Cassini orbiter require warmth and power.

Plutonium pellets are the obvious choice, according to NASA. The radioactive generators have no moving parts, are highly reliable and long-lasting, said Department of Energy scientist Beverly Cook. Solar panels to provide the same energy would be the size of tennis courts and weigh thousands of pounds, too much to lift off the Earth.

At NASA headquarters in Washington Wednesday, Cook instructed the press in the safety of the system, stressing that she planned to take her family to watch the launch.

The plutonium pellets--the size of a stack of quarters--sit inside deformable graphite blocks designed to take any impact. The natural radioactivity of plutonium spits out nuclear particles and heats up the block to more than 500 degrees Fahrenheit. That energy is then converted into electricity to power the craft.

“It cannot explode like a bomb,” Cook said. “It must be inhaled in fine particles to harm humans.” A spray of fine particles would be unlikely, she said, because the plutonium is encased in ceramic material that would break up in large chunks. If Cassini should explode on launch, she said, “we expect no health effects.”

In the event that Cassini crashed into Earth during its 1999 fly-by, plutonium could be released into the atmosphere, Cook said. That could cause about 120 cancer deaths over a 50-year period, she said, which would be virtually unnoticed among the millions of other cancer deaths.

City University of New York physicist Michio Kaku countered that is like arguing that people shouldn’t worry about a drive-by shooting in Los Angeles because the city already has a lot of murders.

He and others cite NASA’s own 1995 environmental impact statement, which predicted as many as 5 billion people could be affected if Cassini crashed into Earth.

NASA counters that odds of a fly-by accident are less than a million to one. But since there have only been several dozen fly-bys, Kaku counters that that statistic is bogus. “If I were giving a physics class, I’d flunk them.”

The truth, said Kaku, is that he doesn’t know what the risk is. “I’m not saying they’re liars. I’m saying they should admit they don’t know too.”